1. Field of the Present Invention
The present invention relates generally to a torque transfer mechanism having plural outputs, and more particularly to an adjustment mechanism for controlling the actuation and the speeds of each output.
2. Description of the Prior Art
The application of power from a vehicle engine to the wheels of more than one axle set in a motor vehicle is accomplished by coupling a transfer case to the output of the vehicle transmission. An input shaft of the transfer case is coupled to the output shaft of the transmission and is selectively connected through power paths formed by gear mechanisms to at least one of two output shafts. Each output shaft is coupled to a respective axle driving mechanism. It has also been known to provide a plurality of power paths through which the torque from the input shaft can be split or modified as desired before it is applied to any of the output shafts of the transfer case.
In previously known transfer cases, it has been common to incorporate constant mesh gearing. In such devices, clutch collars are shiftable for selective engagement with the gears of the desired power path. However, such clutches can increase the size of the transfer case, especially when the collar must be shifted a substantial distance in order to interconnect the input shaft with the various gear sets.
In addition, it has been known to interconnect the clutch collar so that a single operating means can shift more than one collar in order to actuate or adjust the speed of each output shaft. For example, U.S. Pat. No. 4,270,409 discloses a transfer case to be used in a four-wheel drive vehicle which provides both high speed and low speed power paths to the front and rear axles of a vehicle. The transfer case includes a pair of simultaneously shiftable clutch collars operated by means of a single shift fork. The clutch arrangement includes a high speed shift collar and a low speed shift collar. However, the low speed shift collar is slideable along an intermediate gear set having a driven gear which is in constant mesh with a drive gear secured for rotation with the input shaft. As a result, even though the low speed gear set is disengaged from the output shafts, the driven gear of the low speed path continues to operate. As a result, energy losses can be sustained in the low speed power path even though the transfer case is driving one or more of the axles at a high speed. Such movement of the driven gear can contribute to excessive wear on the parts and substantially increases the need for lubrication. Moreover, since the clutch collars are located in the same plane for simultaneous shifting along radially spaced axes, each clutch collar is subjected to greater off-axis moments during shifting than a shift collar or collars displaceable along a single axis.